延时注入跨库注入

思路：

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| challenges         |
| mysql              |
| performance_schema |
| phpmyadmin         |
| ro1                |
| security           |
+--------------------+
7 rows in set (0.01 sec)

mysql> select * from information_schema;
ERROR 1046 (3D000): No database selected
mysql> use ro1;#随便用一个数据库
Database changed

+--------------+--------------------+----------------------------+------------------------+----------+
| CATALOG_NAME | SCHEMA_NAME        | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL_PATH |
+--------------+--------------------+----------------------------+------------------------+----------+
| def          | information_schema | utf8                       | utf8_general_ci        | NULL     |
| def          | challenges         | gbk                        | gbk_chinese_ci         | NULL     |
| def          | mysql              | latin1                     | latin1_swedish_ci      | NULL     |
| def          | performance_schema | utf8                       | utf8_general_ci        | NULL     |
| def          | phpmyadmin         | utf8                       | utf8_bin               | NULL     |
| def          | ro1                | utf8                       | utf8_general_ci        | NULL     |
| def          | security           | gbk                        | gbk_chinese_ci         | NULL     |
+--------------+--------------------+----------------------------+------------------------+----------+
7 rows in set (0.00 sec)

mysql> select schema_name from information_schema.schemata limit 1,1;
+-------------+
| schema_name |
+-------------+
| challenges  |
+-------------+
1 row in set (0.00 sec)